Selective iGluR5 receptor antagonists

ABSTRACT

The present invention provides a method of treating or preventing migraine comprising administering to a patient in need thereof an effective amount of a selective iGluR 5  receptor antagonist. The present invention further provides novel compounds functional as selective iGluR 5  receptor antagonists as well as compositions and formulations comprising said selective iGluR 5  receptor antagonists.

BACKGROUND OF THE INVENTION

In the mammalian central nervous system (CNS), the transmission of nerveimpulses is controlled by the interaction between a neurotransmitter,that is released by a sending neuron, and a surface receptor on areceiving neuron, which causes excitation of this receiving neuron.L-Glutamate, which is the most abundant neurotransmitter in the CNS,mediates the major excitatory pathways in mammals, and is referred to asan excitatory amino acid (EAA). The receptors that respond to glutamateare called excitatory amino acid receptors (EAA receptors). See Watkins& Evans, Ann. Rev. Pharmacol. Toxicol., 21, 165 (1981); Monaghan,Bridges, and Cotman, Ann. Rev. Pharmacol. Toxicol., 29, 365 (1989);Watkins, Krogsgaard-Larsen, and Honore, Trans. Pharm. Sci., 11, 25(1990). The excitatory amino acids are of great physiologicalimportance, playing a role in a variety of physiological processes, suchas long-term potentiation (learning and memory), the development ofsynaptic plasticity, motor control, respiration, cardiovascularregulation, and sensory perception.

Excitatory amino acid receptors are classified into two general types.Receptors that are directly coupled to the opening of cation channels inthe cell membrane of the neurons are termed “ionotropic.” This type ofreceptor has been subdivided into at least three subtypes, which aredefined by the depolarizing actions of the selective agonistsN-methyl-D-aspartate (NMDA),α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), and kainicacid (KA). Molecular biological studies have established that AMPAreceptors are composed of subunits (GluR₁-GluR₄), which can assemble toform functional ion channels. Five kainate receptors have beenidentified which are classified as either High Affinity (KA1 and KA2) orLow Affinity (GluR₅, GluR₆, and GluR₇). Bleakman et al., MolecularPharmacology, 49, No. 4, 581,(1996).

The second general type of receptor is the G-protein or secondmessenger-linked “metabotropic” excitatory amino acid receptor. Thissecond type is coupled to multiple second messenger systems that lead toenhanced phosphoinositide hydrolysis, activation of phospholipase D,increases or decreases in cAMP formation, and changes in ion channelfunction. Schoepp and Conn, Trends in Pharmacol. Sci., 14, 13 (1993).Both types of receptors appear not only to mediate normal synaptictransmission along excitatory pathways, but also to participate in themodification of synaptic connections during development and throughoutlife. Schoepp, Bockaert, and Sladeczek, Trends in Pharmacol. Sci., 11,508 (1990); McDonald and Johnson, Brain Research Reviews, 15, 41 (1990).

The excessive or inappropriate stimulation of excitatory amino acidreceptors leads to neuronal cell damage or loss by way of a mechanismknown as excitotoxicity. This process has been suggested to mediateneuronal degeneration in a variety of neurological disorders andconditions. The medical consequences of such neuronal degeneration makesthe abatement of these degenerative neurological processes an importanttherapeutic goal.

Excitatory amino acid excitotoxicity has been implicated in thepathophysiology of numerous neurological disorders. For example,excitotoxicity has been linked with the etiology of cerebral deficitssubsequent to cardiac bypass surgery and grafting, stroke, cerebralischemia, spinal cord lesions resulting from trauma or inflammation,perinatal hypoxia, cardiac arrest, and hypoglycemic neuronal damage. Inaddition, excitotoxicity has been implicated in chronicneurodegenerative conditions including Alzheimer's Disease, Huntington'sChorea, inherited ataxias, AIDS-induced dementia, amyotrophic lateralsclerosis, idiopathic and drug-induced Parkinson's Disease, as well asocular damage and retinopathy. Other neurological disorders implicatedwith excitotoxicity and/or glutamate dysfunction include muscularspasticity including tremors, drug tolerance and withdrawal, brainedema, convulsive disorders including epilepsy, depression, anxiety andanxiety related disorders such as post-traumatic stress syndrome,tardive dyskinesia, and psychosis related to depression, schizophrenia,bipolar disorder, mania, and drug intoxication or addiction. Inaddition, it has also been reported that excitatory amino acidexcitotoxicity participates in the etiology of acute and chronic painstates including severe pain, intractable pain, neuropathic pain, andpost-traumatic pain.

The use of a neuroprotective agent, such as an excitatory amino acidreceptor antagonist, is believed to be useful in treating or preventingthese disorders and/or reducing the amount of neurological damageassociated with these disorders. Excitatory amino acid receptorantagonists may also be useful as analgesic agents.

Early theories regarding the pathophysiology of migraine have beendominated since 1938 by the work of Graham and Wolff (Arch. Neurol.Psychiatry, 39, 737-63 (1938)). They proposed that the cause of migraineheadache is vasodilatation of extracranial vessels. This view issupported by knowledge that ergot alkaloids and sumatriptan contractcephalic vascular smooth muscle and are effective in the treatment ofmigraine. Sumatriptan is a hydrophilic agonist at the serotonin5-HT-1-like receptors and does not cross the blood-brain barrier(Humphrey, et al., Ann. NY Acad. Sci., 600, 587-600 (1990)).Consequently, several series of compounds said to be useful for thetreatment of migraine, have been developed to optimize the 5-HT₁-likemediated vasoconstrictive activity of sumatriptan. However,sumatriptan's contraindications, including coronary vasospasm,hypertension, and angina are also products of its vasoconstrictiveactivity (MacIntyre, P. D., et al., British Journal of ClinicalPharmacology, 34, 541-546 (1992); Chester, A. H., et al., CardiovascularResearch, 24, 932-937 (1990); Conner, H. E., et al., European Journal ofPharmacology, 161, 91-94 (1990)).

While the vascular mechanism for migraine has gained wide acceptance,there is not total agreement as to its validity. Moskowitz, for example,has shown the occurrence of migraine headaches, independent of changesin vessel diameter (Cephalalgia, 12, 5-7, (1992)). It is known that thetrigeminal ganglion, and its associated nerve pathways, are associatedwith painful sensations from the face such as headache, in particularmigraine. Moskowitz proposed that unknown triggers stimulate thetrigeminal ganglia which innervate vasculature within cephalic tissue,giving rise to the release of vasoactive neuropeptides from axonsinnervating the vasculature. These neuropeptides initiate a series ofevents leading to neurogenic inflammation of the meninges, a consequenceof which is pain. This neurogenic inflammation is blocked by sumatriptanat doses similar to those required to treat acute migraine in humans.However, such doses of sumatriptan, as stated, are associated withcontraindications as a result of sumatriptan's attendantvasoconstrictive properties.(see supra.)

⁵-HT_(1D) receptors have been implicated as mediating the blockade ofneurogenic protein extravasation. (Neurology, 43(suppl. 3), S16-S20(1993)). In addition, it has been reported that α₂, H₃, m-opioid andsomatostatin receptors may also be located on trigeminovascular fibersand may block neurogenic plasma extravasation (Matsubara et al., Eur. J.Pharmacol., 224, 145-150 (1992)). Weinshank et al. have reported thatsumatriptan and several ergot alkaloids have a high affinity for theserotonin ⁵-HT_(1F) receptor, suggesting a role for the ⁵-HT_(1F)receptor in migraine (WO93/14201).

European Patent Application Publication No. 590789A1 and U.S. Pat. Nos.5,446,051 and 5,670,516 disclose that certain decahydroisoquinolinederivative compounds are AMPA receptor antagonists and, as such, areuseful in the treatment of many different conditions, including pain andmigraine headache.

Recently, it has been reported that all five members of the kainatesubtype, of ionotropic glutamate receptors, are expressed on rattrigeminal ganglion neurons. In particular, high levels of GluR₅ and KA2have been observed. (Sahara et al., The Journal of Neuroscience, 17(17),6611 (1997)). Simmons et al. reported that the kainate GluR₅ receptorsubtype mediates the nociceptive response to formalin in a rat model ofpersistent pain.(Neuropharmacology, 37, 25 (1998). Further, WO98/45270previously disclosed that antagonists selective for the iGluR₅ receptorare useful for the treatment of pain, including; severe, chronic,intractable, and neuropathic pain. Noteworthy is the observation thatkainate receptors have not previously been implicated in the etiology ofmigraine headache. In particular, selective iGluR₅ receptor antagonistshave not been previously reported as being useful for the treatment ofmigraine.

Surprisingly, and in accordance with this invention, Applicants havediscovered that selective antagonists of the iGluR₅ receptor subtype areefficacious in an animal model of neurogenic inflammation and, thus,could be useful for the treatment of migraine. Such antagonists couldaddress a long felt need for a safe and effective treatment formigraine, without attending side effects. The treatment of neurologicaldisorders is hereby furthered.

SUMMARY OF THE INVENTION

The present invention provides a method of treating or preventingmigraine comprising administering to a patient in need thereof aneffective amount of a selective iGluR₅ receptor antagonist or apharmaceutically acceptable salt thereof.

More specifically, the present invention provides a method of treatingor preventing dural protein extravasation comprising administering to apatient in need thereof an effective amount of a selective iGluR₅receptor antagonist.

In addition, the present invention provides a method of treating orpreventing migraine comprising administering to a patient in needthereof an effective amount of a compound, or combination of compounds,which possesses the activity of a selective iGluR₅ receptor antagonist.

In another embodiment, the present invention provides a method oftreating or preventing a neurological disorder, or neurodegenerativecondition, comprising administering to a patient in need thereof aneffective amount of a selective iGluR₅ receptor antagonist or apharmaceutically acceptable salt thereof. Examples of such neurologicaldisorders, or neurodegenerative conditions, include: cerebral deficitssubsequent to cardiac bypass surgery and grafting; stroke; cerebralischemia; spinal cord lesions resulting from trauma or inflammation;perinatal hypoxia; cardiac arrest; hypoglycemic neuronal damage;Alzheimer's Disease; Huntington's Chorea; inherited ataxias;AIDS-induced dementia; amyotrophic lateral sclerosis; idiopathic anddrug-induced Parkinson's Disease; ocular damage and retinopathy;muscular spasticity including tremors; drug tolerance and withdrawal;brain edema; convulsive disorders including epilepsy; depression;anxiety and anxiety related disorders such as post-traumatic stresssyndrome; tardive dyskinesia; psychosis related to depression,schizophrenia, bipolar disorder, mania, and drug intoxication oraddiction; and acute and chronic pain states including severe pain,intractable pain, neuropathic pain, and post-traumatic pain.

In a further aspect, the present invention provides a compound ofFormula I

wherein R¹ and R² are each independently H, C₁-C₂₀ alkyl, C₂-C₆ alkenyl,C₁-C₆ alkylaryl, C₁-C₆ alkyl(C₃-C₁₀)cycloalkyl, C₁-C₆ alkyl-N,N—C₁-C₆dialkylamine, C₁-C₆ alkyl-pyrrolidine, C₁-C₆ alkyl-piperidine, or C₁-C₆alkyl-morpholine; or a pharmaceutically acceptable salt thereof.

In yet another aspect, the present invention provides a method oftreating or preventing migraine comprising administering to a patient inneed thereof an effective amount of a compound of Formula I.

In addition, the present invention provides pharmaceutical compositionsuseful for treating or preventing migraine comprising selective iGluR₅receptor antagonists in combination with one or more pharmaceuticallyacceptable carriers, diluents, or excipients.

The present invention also provides the use of a selective iGluR₅receptor antagonist for the manufacture of a medicament for treating orpreventing migraine.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method for the treatment of migrainewhich can be demonstrated by a particular mechanism of action,inhibition of neurogenic dural protein extravasation. By treating amigraineur with a compound or composition which is a selectiveantagonist of the iGluR₅ receptor relative to other excitatory aminoacid receptors, the neurogenic extravasation which mediates migraine isinhibited without the attending side effects of agents designed tooptimize the 5-HT₁-like mediated vasoconstrictive activity ofsumatriptan. In addition, the present invention provides compoundsfunctional as selective iGluR₅ receptor antagonists as well aspharmaceutically acceptable salts, prodrugs, and compositions thereof.

The term “pharmaceutically acceptable salt” as used herein, refers tosalts of the compounds provided by, or employed in the present inventionwhich are substantially non-toxic to living organisms. Typicalpharmaceutically acceptable salts include those salts prepared byreaction of the compounds of the present invention with apharmaceutically acceptable mineral or organic acid or an organic orinorganic base. Such salts are known as acid addition and base additionsalts.

It will be understood by the skilled reader that most or all of thecompounds used in the present invention are capable of forming salts,and that the salt forms of pharmaceuticals are commonly used, oftenbecause they are more readily crystallized and purified than are thefree bases. In all cases, the use of the pharmaceuticals describedherein as salts is contemplated in the description herein, and often ispreferred, and the pharmaceutically acceptable salts of all of thecompounds are included in the names of them.

Acids commonly employed to form acid addition salts are inorganic acidssuch as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuricacid, phosphoric acid, and the like, and organic acids such asp-toluenesulfonic, methanesulfonic acid, oxalic acid,p-bromophenylsulfonic acid, carbonic acid, succinic acid, citric acid,benzoic acid, acetic acid, and the like. Examples of suchpharmaceutically acceptable salts are the sulfate, pyrosulfate,bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate,dihydrogenphosphate, metaphosphate, pyrophosphate, bromide, iodide,acetate, propionate, decanoate, caprylate, acrylate, formate,hydrochloride, dihydrochloride, isobutyrate, caproate, heptanoate,propiolate, oxalate, malonate, succinate, suberate, sebacate, fumarate,maleate, butyne-1,4-dioate, hexyne-1,6-dioate, benzoate, chlorobenzoate,methylbenzoate, hydroxybenzoate, methoxybenzoate, phthalate,xylenesulfonate, phenylacetate, phenylpropionate, phenylbutyrate,citrate, lactate, α-hydroxybutyrate, glycolate, tartrate,methanesulfonate, propanesulfonate, naphthalene-1-sulfonate,napththalene-2-sulfonate, mandelate and the like. Preferredpharmaceutically acceptable acid addition salts are those formed withmineral acids such as hydrochloric acid and hydrobromic acid, and thoseformed with organic acids such as maleic acid and methanesulfonic acid.

Base addition salts include those derived from inorganic bases, such asammonium or alkali or alkaline earth metal hydroxides, carbonates,bicarbonates, and the like. Such bases useful in preparing the salts ofthis invention thus include sodium hydroxide, potassium hydroxide,ammonium hydroxide, potassium carbonate, sodium carbonate, sodiumbicarbonate, potassium bicarbonate, calcium hydroxide, calciumcarbonate, and the like. The potassium and sodium salt forms areparticularly preferred.

It should be recognized that the particular counterion forming a part ofany salt of this invention is usually not of a critical nature, so longas the salt as a whole is pharmacologically acceptable and as long asthe counterion does not contribute undesired qualities to the salt as awhole.

As used herein, the term “stereoisomer” refers to a compound made up ofthe same atoms bonded by the same bonds but having differentthree-dimensional structures which are not interchangeable. Thethree-dimensional structures are called configurations. As used herein,the term “enantiomer” refers to two stereoisomers whose molecules arenonsuperimposable mirror images of one another. The term “chiral center”refers to a carbon atom to which four different groups are attached. Asused herein, the term “diastereomers” refers to stereoisomers which arenot enantiomers. In addition, two diastereomers which have a differentconfiguration at only one chiral center are referred to herein as“epimers”. The terms “racemate”, “racemic mixture” or “racemicmodification” refer to a mixture of equal parts of enantiomers.

The term “enantiomeric enrichment” as used herein refers to the increasein the amount of one enantiomer as compared to the other. A convenientmethod of expressing the enantiomeric enrichment achieved is the conceptof enantiomeric excess, or “ee”, which is found using the followingequation: ${ee} = {\frac{E^{1} - E^{2}}{E^{1} + E^{2}} \times 100}$wherein E¹ is the amount of the first enantiomer and E² is the amount ofthe second enantiomer. Thus, if the initial ratio of the two enantiomersis 50:50, such as is present in a racemic mixture, and an enantiomericenrichment sufficient to produce a final ratio of 50:30 is achieved, theee with respect to the first enantiomer is 25%. However, if the finalratio is 90:10, the ee with respect to the first enantiomer is 80%. Anee of greater than 90% is preferred, an ee of greater than 95% is mostpreferred and an ee of greater than 99% is most especially preferred.Enantiomeric enrichment is readily determined by one of ordinary skillin the art using standard techniques and procedures, such as gas or highperformance liquid chromatography with a chiral column. Choice of theappropriate chiral column, eluent and conditions necessary to effectseparation of the enantiomeric pair is well within the knowledge of oneof ordinary skill in the art. In addition, the enantiomers of compoundsof formula I can be resolved by one of ordinary skill in the art usingstandard techniques well known in the art, such as those described by J.Jacques, et al., “Enantiomers, Racemates, and Resolutions”, John Wileyand Sons, Inc., 1981.

The compounds of the present invention have one or more chiral centersand may exist in a variety of stereoisomeric configurations. As aconsequence of these chiral centers, the compounds of the presentinvention occur as racemates, mixtures of enantiomers and as individualenantiomers, as well as diastereomers and mixtures of diastereomers. Allsuch racemates, enantiomers, and diastereomers are within the scope ofthe present invention.

The terms “R” and “S” are used herein as commonly used in organicchemistry to denote specific configuration of a chiral center. The term“R” (rectus) refers to that configuration of a chiral center with aclockwise relationship of group priorities (highest to second lowest)when viewed along the bond toward the lowest priority group. The term“S” (sinister) refers to that configuration of a chiral center with acounterclockwise relationship of group priorities (highest to secondlowest) when viewed along the bond toward the lowest priority group. Thepriority of groups is based upon their atomic number (in order ofdecreasing atomic number). A partial list of priorities and a discussionof stereochemistry is contained in “Nomenclature of Organic Compounds:Principles and Practice”, (J. H. Fletcher, et al., eds., 1974) at pages103-120.

The specific stereoisomers and enantiomers of compounds of Formula (I)can be prepared by one of ordinary skill in the art utilizing well knowntechniques and processes, such as those disclosed by Eliel and Wilen,“Stereochemistry of Organic Compounds”, John Wiley & Sons, Inc., 1994,Chapter 7, Separation of Stereoisomers. Resolution. Racemization, and byCollet and Wilen, “Enantiomers, Racemates, and Resolutions”, John Wiley& Sons, Inc., 1981. For example, the specific stereoisomers andenantiomers can be prepared by stereospecific syntheses usingenantiomerically and geometrically pure, or enantiomerically orgeometrically enriched starting materials. In addition, the specificstereoisomers and enantiomers can be resolved and recovered bytechniques such as chromatography on chiral stationary phases, enzymaticresolution or fractional recrystallization of addition salts formed byreagents used for that purpose.

It should also be understood by the skilled artisan that all of thecompounds useful for the methods of the present invention are availablefor prodrug formualtion. “Prodrug” as used herein, refers tometabolically labile ester or diester derivative of the functional acidcompounds(drugs) provided by, or employed in the methods of, the presentinvention. When administered to a patient, the prodrug undergoesenzymatic and/or chemical hydrolytic cleavage in such a manner that theparent carboxylic acid (drug), or as the case may be the parentdicarboxylic acid, is released. In all cases, the use of the compoundsdescribed herein as prodrugs is contemplated, and often is preferred,and thus, the prodrugs of all of the compounds employed are encompassedin the names of the compounds herein.

As used herein the term “C₁-C₄ alkyl” refers to a straight or branched,monovalent, saturated aliphatic chain of 1 to 4 carbon atoms andincludes, but is not limited to methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl and the like.

As used herein the term “C₁-C₆ alkyl” refers to a straight or branched,monovalent, saturated aliphatic chain of 1 to 6 carbon atoms andincludes, but is not limited to methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, and the like.

As used herein the term “C₁-C₁₀ alkyl” refers to a straight or branched,monovalent, saturated aliphatic chain of 1 to 10 carbon atoms andincludes, but is not limited to methyl, ethyl, propyl, isopropyl,n-butyl, isobutyl, tertiary butyl, pentyl, isopentyl, hexyl,2,3-dimethyl-2-butyl, heptyl, 2,2-dimethyl-3-pentyl, 2-methyl-2-hexyl,octyl, 4-methyl-3-heptyl and the like.

As used herein the term “C₁-C₂₀ alkyl” refers to a straight or branched,monovalent, saturated aliphatic chain of 1 to 20 carbon atoms andincludes, but is not limited to, methyl, ethyl, propyl, isopropyl,butyl, isobutyl, t-butyl, pentyl, isopentyl, hexyl, 3-methylpentyl,2-ethylbutyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl,n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl,n-nonadecyl, n-eicosyl and the like.

As used herein, the terms “Me”, “Et”, “Pr”, “iPr”, “Bu” and “t-Bu” referto methyl, ethyl, propyl, isopropyl, butyl and tert-butyl respectively.

As used herein the term “C₂-C₆ alkenyl” refers to a straight orbranched, monovalent, unsaturated aliphatic chain having from two to sixcarbon atoms. Typical C₂-C₆ alkenyl groups include ethenyl (also knownas vinyl), 1-methylethenyl, 1-methyl-1-propenyl, 1-butenyl, 1-hexenyl,2-methyl-2-propenyl, 1-propenyl, 2-propenyl, 2-butenyl, 2-pentenyl, andthe like.

As used herein, the term “aryl” refers to monovalent carbocyclic groupcontaining one or more fused or non-fused phenyl rings and includes, forexample, phenyl, 1- or 2-naphthyl, 1,2-dihydronaphthyl,1,2,3,4-tetrahydronaphthyl, and the like.

As used herein, the term “C₁-C₆ alkylaryl” refers to a straight orbranched, monovalent, saturated aliphatic chain of 1 to 6 carbon atomswhich has an aryl group attached to the aliphatic chain. Included withinthe term “C₁-C₆ alkylaryl” are the following:

and the like.

As used herein the term “(C₃-C₁₀)cycloalkyl” refers to a saturatedhydrocarbon ring structure containing from three to ten carbon atoms.Typical C₃-C₁₀ cycloalkyl groups include cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and the like. It isunderstood that “(C₃-C₈)cycloalkyl” and “(C₄-C₆)cycloalkyl” is includedwithin the term “(C₃-C₁₀)cycloalkyl”.

As used herein, the term “C₁-C₆ alkyl(C₃-C₁₀)cycloalkyl” refers to astraight or branched, monovalent, saturated aliphatic chain of 1 to 6carbon atoms which has a (C₃-C₁₀)cycloalkyl attached to the aliphaticchain. Included within the term “C₁-C₆ alkyl(C₃-C₁₀)cycloalkyl” are thefollowing:

and the like.

As used herein the term “N,N—C₁-C₆ dialkylamine” refers to a nitrogenatom substituted with two straight or branched, monovalent, saturatedaliphatic chains of 1 to 6 carbon atoms. Included within the term“N,N—C₁-C₆ dialkylamine” are —N(CH₃)₂, —N(CH₂CH₃)₂, —N(CH₂CH₂CH₃)₂,—N(CH₂CH₂CH₂CH₃)₂, and the like.

As used herein the term “C₁-C₆ alkyl-N,N—C₁-C₆ dialkylamine” refers tostraight or branched, monovalent, saturated aliphatic chain of 1 to 6carbon atoms which has an N,N—C₁-C₆ dialkylamine attached to thealiphatic chain. Included within the term “C₁-C₆ alkyl-N,N—C₁-C₆dialkylamine” are the following:

and the like.

As used herein the term “C₁-C₆ alkyl-pyrrolidine” refers to a straightor branched, monovalent, saturated aliphatic chain of 1 to 6 carbonatoms which has a pyrrolidine attached to the aliphatic chain. Includedwithin the scope of the term “C₁-C₆ alkyl-pyrrolidine” are thefollowing:

and the like.

As used herein the term “C₁-C₆ alkyl-piperidine” refers to a straight orbranched, monovalent, saturated aliphatic chain of 1 to 6 carbon atomswhich has a piperidine attached to the aliphatic chain. Included withinthe scope of the term “C₁-C₆ alkyl-piperidine” are the following:

and the like.

As used herein the term “C₁-C₆ alkyl-morpholine” refers to a straight orbranched, monovalent, saturated aliphatic chain of 1 to 6 carbon atomswhich has a morpholine attached to the aliphatic chain. Included withinthe scope of the term “C₁-C₆ alkyl-morpholine” are the following:

and the like.

The designation

refers to a bond that protrudes forward out of the plane of the page.

The designation

refers to a bond that protrudes backward out of the plane of the page.

As used herein the term “iGluR₅” refers to the kainate ionotropicglutamate receptor, subtype 5, of the larger class of excitatory aminoacid receptors.

As used herein the term “migraine” refers a disorder of the nervoussystem characterized by recurrent attacks of head pain (which are notcaused by a structural brain abnormalitiy such as those resulting fromtumor or stroke), gasrointestinal disturbances, and possiblyneurological symptoms such as visual distortion. Characteristicheadaches of migraine usually last one day and are commonly accompaniedby nausea, emesis, and photophobia.

Migraine is a “chronic” condition. The term “chronic”, as used herein,means a condition of slow progress and long continuance. As such, achronic condition is treated when it is diagnosed and treatmentcontinued throughout the course of the disease. Conversely, the term“acute” means an exacerbated event or attack, of short course, followedby a period of remission. Thus, the treatment of migraine contemplatesboth acute events and chronic conditions. In an acute event, compound isadministered at the onset of symptoms and discontinued when the symptomsdisappear. As described above, a chronic condition is treated throughoutthe course of the disease.

As used herein the term “patient” refers to a mammal, such a mouse,gerbil, guinea pig, rat, dog or human. It is understood, however, thatthe preferred patient is a human.

It is understood that the term “selective iGluR₅ receptor antagonist” asused herein, includes those excitatory amino acid receptor antagonistswhich selectively bind to the iGluR₅ kainate receptor subtype, relativeto the iGluR₂ AMPA receptor subtype. Preferably the selective iGluR₅antagonist for use according to the method of the present invention hasa binding affinity at least 10 fold greater for iGluR₅ than for iGluR₂,more preferably at least 100 fold greater. It is further understood thatany selective iGluR₅ antagonist, as appreciated by one of ordinary skillin the art, is included within the scope of the methods of the presentinvention. Such selective iGluR₅ receptor antagonists are readilyavailable to, or are readily prepared by, one of ordinary skill in theart following recognized procedures. Examples of selective iGluR₅receptor antagonists include, but are not limited to, the compoundsprovided in WO 98/45270, the entire contents of which is hereinincorporated by reference.

It is further understood that the selective iGluR₅ receptor antagonistsmay exist as pharmaceutically acceptable salts and, as such, salts aretherefore included within the scope of the present invention.

As used herein, the terms “treating” or “to treat” each mean toalleviate symptoms, eliminate the causation of resultant symptoms eitheron a temporary or permanent basis, and to prevent, slow the appearance,or reverse the progression or severity of resultant symptoms of thenamed disorder. As such, the methods of this invention encompass boththerapeutic and prophylactic administration.

As used herein the term “effective amount” refers to the amount or doseof the compound, upon single or multiple dose administration to thepatient, which provides the desired effect in the patient underdiagnosis or treatment.

An effective amount can be readily determined by the attendingdiagnostician, as one skilled in the art, by the use of known techniquesand by observing results obtained under analogous circumstances. Indetermining the effective amount or dose of compound administered, anumber of factors are considered by the attending diagnostician,including, but not limited to: the species of mammal; its size, age, andgeneral health; the degree of involvement or the severity of themigraine involved; the response of the individual patient; theparticular compound administered; the mode of administration; thebioavailability characteristics of the preparation administered; thedose regimen selected; the use of concomitant medication; and otherrelevant circumstances.

A typical daily dose will contain from about 0.01 mg/kg to about 100mg/kg of each compound used in the present method of treatment.Preferably, daily doses will be about 0.05 mg/kg to about 50 mg/kg, morepreferably from about 0.1 mg/kg to about 25 mg/kg.

The selective iGluR₅ antagonists for use according to the methods of thepresent invention may be a single compound or a combination of compoundscapable of functioning as a selective iGluR₅ receptor antagonist. Forexample, it may be a combination of a compound capable of functioning asan antagonist at the iGluR₅ receptor and one or more other glutamatereceptors, in combination with one or more compounds capable of blockingits actions at the iGluR₂ receptor. It is understood, however, that theselective iGluR₅ antagonist for use in the methods of the presentinvention, is preferably a single compound.

Oral administration is a preferred route of administering the compoundsemployed in the present invention whether administered alone, or as acombination of compounds capable of acting as a selective iGluR₅receptor antagonist. Oral administration, however, is not the onlyroute, nor even the only preferred route. Other preferred routes ofadministration include transdermal, percutaneous, intravenous,intramuscular, intranasal, buccal, or intrarectal routes. Where theselective iGluR₅ receptor antagonist is administered as a combination ofcompounds, one of the compounds may be administered by one route, suchas oral, and the other may be administered by the transdermal,percutaneous, intravenous, intramuscular, intranasal, buccal, orintrarectal route, as particular circumstances require. The route ofadministration may be varied in any way, limited by the physicalproperties of the compounds and the convenience of the patient and thecaregiver.

The compounds employed in the present invention may be administered aspharmaceutical compositions and, therefore, pharmaceutical compositionsincorporating said compounds are important embodiments of the presentinvention. Such compositions may take any physical form which ispharmaceutically acceptable, but orally administered pharmaceuticalcompositions are particularly preferred. Such pharmaceuticalcompositions contain an effective amount of a selective iGluR₅ receptorantagonist, which effective amount is related to the daily dose of thecompound to be administered. Each dosage unit may contain the daily doseof a given compound, or may contain a fraction of the daily dose, suchas one-half or one-third of the dose. The amount of each compound to becontained in each dosage unit depends on the identity of the particularcompound chosen for the therapy, and other factors such as theindication for which it is given. The pharmaceutical compositions of thepresent invention may be formulated so as to provide quick, sustained,or delayed release of the active ingredient after administration to thepatient by employing well known procedures.

Compositions are preferably formulated in a unit dosage form, eachdosage containing from about 1 to about 500 mg of each compoundindividually or in a single unit dosage form, more preferably about 5 toabout 300 mg (for example 25 mg). The term “unit dosage form” refers toa physically discrete unit suitable as unitary dosages for a patient,each unit containing a predetermined quantity of active materialcalculated to produce the desired therapeutic effect, in associationwith a suitable pharmaceutical carrier, diluent, or excipient.

The inert ingredients and manner of formulation of the pharmaceuticalcompositions are conventional. The usual methods of formulation used inpharmaceutical science may be used here. All of the usual types ofcompositions may be used, including tablets, chewable tablets, capsules,solutions, parenteral solutions, intranasal sprays or powders, troches,suppositories, transdermal patches and suspensions. In general,compositions contain from about 0.5% to about 50% of the compounds intotal, depending on the desired doses and the type of composition to beused. The amount of the compound, however, is best defined as the“effective amount”, that is, the amount of each compound which providesthe desired dose to the patient in need of such treatment. The activityof the compounds employed in the present invention do not depend on thenature of the composition, hence, the compositions are chosen andformulated solely for convenience and economy.

Capsules are prepared by mixing the compound with a suitable diluent andfilling the proper amount of the mixture in capsules. The usual diluentsinclude inert powdered substances such as starches, powdered celluloseespecially crystalline and microcrystalline cellulose, sugars such asfructose, mannitol and sucrose, grain flours, and similar ediblepowders.

Tablets are prepared by direct compression, by wet granulation, or bydry granulation. Their formulations usually incorporate diluents,binders, lubricants and disintegrators as well as the compound. Typicaldiluents include, for example, various types of starch, lactose,mannitol, kaolin, calcium phosphate or sulfate, inorganic salts such assodium chloride and powdered sugar. Powdered cellulose derivatives arealso useful. Typical tablet binders are substances such as starch,gelatin and sugars such as lactose, fructose, glucose and the like.Natural and synthetic gums are also convenient, including acacia,alginates, methylcellulose, polyvinylpyrrolidine and the like.Polyethylene glycol, ethylcellulose and waxes can also serve as binders.

Tablets are often coated with sugar as a flavor and sealant. Thecompounds may also be formulated as chewable tablets, by using largeamounts of pleasant-tasting substances such as mannitol in theformulation, as is now well-established practice. Instantly dissolvingtablet-like formulations are also now frequently used to assure that thepatient consumes the dosage form, and to avoid the difficulty inswallowing solid objects that bothers some patients.

A lubricant is often necessary in a tablet formulation to prevent thetablet and punches from sticking in the die. The lubricant is chosenfrom such slippery solids as talc, magnesium and calcium stearate,stearic acid and hydrogenated vegetable oils.

Tablet disintegrators are substances which swell when wetted to break upthe tablet and release the compound. They include starches, clays,celluloses, algins and gums. More particularly, corn and potatostarches, methylcellulose, agar, bentonite, wood cellulose, powderednatural sponge, cation-exchange resins, alginic acid, guar gum, citruspulp and carboxymethylcellulose, for example, may be used, as well assodium lauryl sulfate.

Enteric formulations are often used to protect an active ingredient fromthe strongly acid contents of the stomach. Such formulations are createdby coating a solid dosage form with a film of a polymer which isinsoluble in acid environments, and soluble in basic environments.Exemplary films are cellulose acetate phthalate, polyvinyl acetatephthalate, hydroxypropyl methylcellulose phthalate and hydroxypropylmethylcellulose acetate succinate.

When it is desired to administer the compound as a suppository, theusual bases may be used. Cocoa butter is a traditional suppository base,which may be modified by addition of waxes to raise its melting pointslightly. Water-miscible suppository bases comprising, particularly,polyethylene glycols of various molecular weights are in wide use, also.

Transdermal patches have become popular recently. Typically theycomprise a resinous composition in which the drugs will dissolve, orpartially dissolve, which is held in contact with the skin by a filmwhich protects the composition. Many patents have appeared in the fieldrecently. Other, more complicated patch compositions are also in use,particularly those having a membrane pierced with innumerable poresthrough which the drugs are pumped by osmotic action.

The following table provides an illustrative list of formulationssuitable for use with the compounds employed in the present invention.The following is provided only to illustrate the invention and shouldnot be interpreted as limiting the present invention in any way.Formulation 1 Hard gelatin capsules are prepared using the followingingredients: Quantity (mg/capsule) Active Ingredient 250 Starch, dried200 Magnesium stearate 10 Total 460 mg

The above ingredients are mixed and filled into hard gelatin capsules in460 mg quantities. Formulation 2 A tablet is prepared using theingredients below: Quantity (mg/tablet) Active Ingredient 250 Cellulose,microcrystalline 400 Silicon dioxide, fumed 10 Stearic acid 5 Total 665mg

The components are blended and compressed to form tablets each weighing665 mg. Formulation 3 An aerosol solution is prepared containing thefollowing components: Weight % Active Ingredient 0.25 Ethanol 29.75Propellant 22 70.00 (Chlorodifluoromethane) Total 100.00

The active compound is mixed with ethanol and the mixture added to aportion of the Propellant 22, cooled to −30° C. and transferred to afilling device. The required amount is then fed to a stainless steelcontainer and diluted with the remainder of the propellant. The valveunits are then fitted to the container. Formulation 4 Tablets eachcontaining 60 mg of active ingredient are made as follows: ActiveIngredient 60 mg Starch 45 mg Microcrystalline cellulose 35 mgPolyvinylpyrrolidone 4 mg Sodium carboxymethyl starch 4.5 mg Magnesiumstearate 0.5 mg Talc 1 mg Total 150 mg

The active ingredient, starch, and cellulose are passed through a No. 45mesh U.S. sieve and mixed thoroughly. The solution ofpolyvinylpyrrolidone is mixed with the resultant powders which are thenpassed through a No. 14 mesh U.S. sieve. The granules so produced aredried at 50° C. and passed through a No. 18 mesh U.S. sieve. The sodiumcarboxymethyl starch, magnesium stearate, and talc, previously passedthrough a No. 60 mesh U.S. sieve, are then added to the granules which,after mixing, are compressed on a tablet machine to yield tablets eachweighing 150 mg. Formulation 5 Capsules each containing 80 mg medicamentare made as follows: Active Ingredient 80 mg Starch 59 mgMicrocrystalline cellulose 59 mg Magnesium stearate 2 mg Total 200 mg

The active ingredient. cellulose, starch, and magnesium stearate areblended, passed through a No. 45 sieve, and filled into hard gelatincapsules in 200 mg quantities. Formulation 6 Suppositories eachcontaining 225 mg of active ingredient may be made as follows: ActiveIngredient 225 mg Saturated fatty acid glycerides 2,000 mg Total 2,225mg

The active ingredient is passed through a No. 60 mesh U.S. sieve andsuspended in the saturated fatty acid glycerides previously melted usingthe minimum heat necessary. The mixture is then poured into asuppository mold of nominal 2 g capacity and allowed to cool.Formulation 7 Suspensions each containing 50 mg of medicament per 5 mldose are made as follows: Active Ingredient   50 mg Sodium carboxymethylcellulose   50 mg Syrup 1.25 ml Benzoic acid solution 0.10 ml Flavorq.v. Color q.v. Purified water to total   5 ml

The medicament is passed through a No. 45 mesh U.S. sieve and mixed withthe sodium carboxymethyl cellulose and syrup to form a smooth paste. Thebenzoic acid solution, flavor and color are diluted with some of thewater and added, with stirring. Sufficient water is then added toproduce the required volume. Formulation 8 An intravenous formulationmay be prepared as follows: Active Ingredient 100 mg Mannitol 100 mg 5 NSodium hydroxide 200 ml Purified water to total  5 ml

It is understood by one of ordinary skill in the art that the aboveprocedures can also be applied to a method of treating migrainecomprising administering to a patient an effective amount of a compoundwhich possesses the activity of a selective iGluR₅ receptor antagonist.

Inhibition of neuronal protein dural extravasation is an exemplarymechanism of action for the method of the present invention. The methodfurther requires that compounds which exhibit such inhibition, alsodemonstrate selective binding and inhibition of the iGluR5 receptor. Thepanel of compounds used to illustrate the principle of the presentinvention, and the pharmacological assays employed to demonstrate themechanistic effectiveness of the invention, are described below. It isbelieved that Compounds III, IV(a), and IV(b) herein, represent novelcompounds and, as such, have not previously been described as selectiveiGluR₅ receptor antagonists, nor reported as efficacious in treatingmigraine. Compounds III, IV(a), and IV(b) therefore, are provided asadditional embodiments of the present invention.

The following examples illustrate the methods of the present invention.The reagents and starting materials are readily available to one ofordinary skill in the art. These examples are intended to beillustrative only and are not to be construed so as to limit the scopeof the invention in any way. As used herein, the following terms havethe meanings indicated: “i.v.” refers to intravenously; “p.o.” refers toorally; “i.p.” refers to intraperitoneally; “eq” or “equiv.” refers toequivalents; “g” refers to grams; “mg” refers to milligrams; “L” refersto liters; “mL” refers to milliliters; “μL” refers to microliters; “mol”refers to moles; “mmol” refers to millimoles; “psi” refers to pounds persquare inch; “mm Hg” refers to millimeters of mercury; “min” refers tominutes; “h” or “hr” refers to hours; “° C.” refers to degrees Celsius;“TLC” refers to thin layer chromatography; “HPLC” refers to highperformance liquid chromatography; “R_(f)” refers to retention factor;“R_(t)” refers to retention time; “δ” refers to part per milliondown-field from tetramethylsilane; “THF” refers to tetrahydrofuran;“DMF” refers to N,N-dimethylformamide; “DMSO” refers to dimethylsulfoxide; “aq” refers to aqueous; “EtOAc” refers to ethyl acetate;“iPrOAc” refers to isopropyl acetate; “MeOH” refers to methanol; “MTBE”refers to tert-butyl methyl ether; “RT” refers to room temperature;“K_(i)” refers to the dissociation constant of an enzyme-antagonistcomplex and serves as an index of ligand binding; and “ID₅₀” and “ID₁₀₀”refer to doses of an administered therapeutic agent which produce,respectively, a 50% and 100% reduction in a physiological response.

EXAMPLE 1 Compound I3S,4aR,6S,8aR-6-(((4-carboxy)phenyl)methyl)-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylicacid

Those skilled in the art will recognize Compound I as an excitatoryamino acid receptor antagonist, selective for the iGluR₅ receptorsubtype. Compound I may be readily prepared by one of ordinary skill inthe art following recognized general procedures as described in U.S.Pat. No. 5,446,051, and more specifically as recently published ininternational application WO 98/45270, published Oct. 15, 1998.

Compound II3S,4aR,6S,8aR-6-((((1H-Tetrazole-5-yl)methyl)oxy)methyl)-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylicacid

Those skilled in the art will recognize Compound II as an excitatoryamino acid receptor antagonist, selective for the iGluR₅ receptorsubtype. Compound II may be readily prepared and resolved by one ofordinary skill in the art following recognized general procedures asdescribed in U.S. Pat. No. 5,670,516 (see Example No. 11, Compound No.7), and more specifically as recently published in internationalapplication WO 98/45270, published Oct. 15, 1998.

Compound III represents a novel compound, functional as a selectiveiGluR₅ receptor antagonist. Compound III may be readily prepared; thedesired enantiomer may be optically resolved; and pharmaceuticalcompositions comprising Compound III may be readily formulated byfollowing general methods essentially as described for Example No. 8,Compound No. 8 of U.S. Pat. No. 5,670,516, the entire contents of whichis herein incorporated by reference.

Compound IV(b) 3S,4aR,6S,8aR Ethyl6-(((2S)-2-(Ethoxycarbonyl)-4,4-difluoropyrrolidinyl)methyl)-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate

A. Preparation of 3S,4aR,6S,8aR Ethyl6-((4-Methylphenyl)sulfonyloxy)methyl)-2-methoxycarbonyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate

To a solution of 15.0 g (50.1 mmol) of hydroxymethyl intermediate (SeeCol.11-12, Scheme II of U.S. Pat. No. 5,356,902, the entire contents ofwhich are herein incorporated by reference) cooled to 0° C. in CH₂Cl₂(100 mL), was added triethylamine (20.9 mL, 150.3 mmol) followed bytoluenesolfonyl chloride (19.1 g, 100.2 mmol) dissolved in CH₂Cl₂ (100mL). The reaction was warmed to room temperature and stirred 16 h, thenpartitioned between CH₂Cl₂ and 10% aqueous NaHSO₄. The aqueous layer wasextracted with CH₂Cl₂ and the combined organics were dried over MgSO₄,filtered, and concentrated in vacuo. Column chromatography (10-50%EtOAc/hexane) provided 20.1 g (89%) of the desired intermediate titlecompound as a colorless oil:

MS(m/e): 451.5 (M⁺)

Calculated for C₂₂H₃₁NO₇S 0.1 CH₂Cl₂: Theory: C, 57.45; H, 6.81; N,3.03. Found: C, 57.76; H, 6.93; N, 3.35.

¹³C NMR (DMSO-d₆): δ 171.4, 144.8, 132.4, 130.1, 127.6, 74.6, 60.4,53.1, 52.4, 44.1, 34.6, 31.8, 31.0, 29.8, 28.8, 24.9, 23.3, 21.0, 14.0.

B. Preparation of 3S,4aR,6S,8aR Ethyl6-(((3S,5S)-5-(Ethoxycarbonyl)-3-hydroxypyrrolidinyl)methyl)-2-methoxycarbonyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate

A mixture of trans 4-hydroxy-L-proline ethyl ester (6.5 g, 33.1 mmol),the compound of Step A above (10.0 g, 22.0 mmol), and potassiumcarbonate (4.6 g, 33.1 mmol) were heated at reflux in acetonitrile (22mL) for 60 h. The reaction mixture was cooled to room temperature, andpartitioned between CH₂Cl₂ and water. The aqueous layer was extractedtwo times with CH₂Cl₂ and the combined organics were dried over MgSO₄,filtered, and concentrated in vacuo. Column chromatography (50%EtOAc/hexane followed by 5% MeOH/CH₂Cl₂) gave 9.2 g (95%) of the desiredintermediate title compound as a colorless oil:

MS(m/e): 441.3 (M⁺)

Calculated for C₂₂H₃₆N₂O₇S: Theory: C, 59.98; H, 8.24; N, 6.36. Found:C, 60.17; H, 8.23; N, 6.42.

C. Preparation of 3S,4aR,6S,8aR Ethyl6-(((5S)-5-(Ethoxycarbonyl)-3-oxopyrrolidinyl)methyl)-2-methoxycarbonyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate

To a solution of DMSO (2.3 mL, 32.5 mmol) cooled to −78° C. in CH₂Cl₂(25 mL) was added, dropwise, oxalyl chloride (1.4 mL, 16.3 mmol). Thereaction mixture was stirred for 5 min, then the compound of Step Babove (6.0 g, 13.6 mmol) dissolved in 20 mL of CH₂Cl₂ was added. Uponstirring for 45 min at −78° C., triethylamine (9.5 mL, 32.5 mmol) wasadded. The reaction was warmed to room temperature over approximately 2hours. and quenched by the addition of 10% aqueous NaHSO₄. The aqueouslayer was extracted with CH₂Cl₂ and the combined organics were driedover MgSO₄, filtered, and concentrated in vacuo. Column chromatography(25-50% EtOAc/hexane) provided 4.6 g (78%) of the desired intermediatetitle compound as a colorless oil:

MS(m/e): 439.1 (M⁺)

D. Preparation of 3S,4aR,6S,8aR Ethyl6-(((2S)-2-(Ethoxycarbonyl)-4,4-difluoropyrrolidinyl)methyl)-2-methoxycarbonyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate

To a mixture of the compound of Step C above (4.62 g, 10.5 mmol) cooledto −78° C. in CH₂Cl₂ (50 mL) was added, dropwise, diethylaminosulfurtrifluoride (3.5 mL, 26.3 mmol). The reaction was allowed to warm toroom temperature, stirred an additional 48 h, then quenched by theaddition of MeOH. After concentrating in vacuo, the residue waspartitioned between CH₂Cl₂ and saturated aqueous NaHCO₃. The aqueouslayer was extracted with CH₂Cl₂ and the combined organics were driedover MgSO₄, filtered, and concentrated in vacuo. Column chromatography(25-50% EtOAc/hexane) provided 3.3 g (68%) of the desired intermediatetitle compound as a colorless oil:

MS(m/e): 461.2 (M⁺)

Calculated for C₂₂H₃₄F₂N₂O₆: Theory: C, 57.38; H, 7.44: N, 6.08. Found:C, 57.28; H, 7.52; N, 6.13.

E. Preparation of 3S,4aR,6S,8aR Ethyl6-(((2S)-2-(Ethoxycarbonyl)-4,4-difluoropyrrolidinyl)methyl)-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate(Compound IV(b))

A solution of the compound of Step D above (3.3 g, 7.10 mmol) dissolvedin CH₂Cl₂ (40 mL) was cooled to 0° C. and charged with trimethylsilyliodide (3.0 mL, 21.3 mmol). The reaction was allowed to warm to roomtemperature, stirred an additional 4 h, then quenched by the addition ofsaturated aqueous NaHCO₃ (50 mL). The aqueous layer was extracted withCH₂Cl₂ and the combined organics washed with a 1 N solution of sodiumthiosulfate, dried over MgSO₄, filtered, and concentrated in vacuo. Thematerial was chromatographed, (2% MeOH/CH₂Cl₂), dissolved in 20 mL ofEt₂O, and to it was added 50 mL of a HCl/Et₂O solution. The solvent wasremoved in vacuo, providing 2.6 g (76%) of the final title compound as awhite solid:

MS(m/e): 403.4 (M⁺)

Calculated for C₂₀H₃₂ Cl₂F₂N₂O₄: Theory: C, 50.53; H, 7.21; N, 5.89.Found: C, 50.90; H, 7.41; N, 5.84.

¹³C NMR (D₂O): δ 170.3, 167.7, 125.1 (t, J_(C-F)=249.1 Hz), 65.9, 65.0,64.1, 63.4, 60.1 (t, J_(C-F)=33.9 Hz), 57.6, 52.8, 42.9, 37.2 (t,J_(C-F)=26.4 Hz), 34.5, 31.7, 31.3, 30.5, 28.4, 26.9, 24.3, 13.6.

Compound IV(a) 3S,4aR,6S,8aR 6-(((2S)-2-(Carboxylicacid)-4,4-difluoropyrrolidinyl)methyl)-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylicAcid

A solution of 3S,4aR,6S,8aR Ethyl6-(((2S)-2-(Ethoxycarbonyl)-4,4-difluoropyrrolidinyl)methyl)-2-methoxycarbonyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate(3.3 g, 7.10 mmol), the compound of Step D above, dissolved in 5 Naqueous HCl (15 mL) was heated at 90° C. for 18 h. The reaction mixturewas cooled to room temperature and concentrated in vacuo. The resultingcrude foam was dissolved in water (75 mL) and stirred in the presence ofDowex 50×8 (100-200) ion-exchange resin (10 g) for 2 h. The resin wasfiltered, washed sequentially with 1:1 THF/H₂O and water, then stirredin the presence of 10% pyridine/H₂O for 2 h. After filtration, the resinwas washed with water, and the filtrate was concentrated in vacuo toprovide the title compound (0.6 g, 97%) as a white foam:

MS(m/e): 347.2 (M⁺)

Calculated for C₁₆H₂₄F₂N₂O₄ 0.1 H₂O: Theory: C, 55.19; H, 7.01; N, 8.05.Found: C, 54.81; H, 6.82; N, 8.13.

¹³C NMR (D₂O): δ 175.1, 171.1, 125.6 (t, J_(C-F)=249.4 Hz), 67.9, 63.0,59.3 (t, J_(C-F)=34.0 Hz), 54.5, 42.5, 37.5 (t, J_(C-F)=24.9 Hz), 34.3,32.7, 32.4, 30.6, 28.2, 27.0, 24.3.

EXAMPLE 2

To establish that the iGluR₅ receptor subtype is mediating neurogenicprotein extravasation, a functional characteristic of migraine, thebinding affinity of the panel compounds to the iGluR₅ receptor is firstmeasured using standard methods. For example, the activity of compoundsacting at the iGluR₅ receptor antagonists can be determined byradiolabelled ligand binding studies at the cloned and expressed humaniGluR5 receptor (Korczak et al., 1994, Recept. Channels 3; 41-49), andby whole cell voltage clamp electrophysiological recordings of currentsin acutely isolated rat dorsal root ganglion neurons (Bleakman et al.,1996, Mol. Pharmacol. 49; 581-585). The selectivity of compounds actingat the iGluR₅ receptor subtype can then be determined by comparingantagonist activity at the iGluR₅ receptor with antagonist activity atother AMPA and kainate receptors. Methods useful for such comparisonstudies include: receptor-ligand binding studies and whole-cell voltageclamp electrophysiological recordings of functional activity at humanGluR₁, GluR₂,GluR₃ and GluR₄ receptors (Fletcher et al., 1995, Recept.Channels 3; 21-31); receptor-ligand binding studies and whole-cellvoltage clamp electrophysiological recordings of functional activity athuman GluR₆ receptors (Hoo et al., Recept. Channels 2;327-338); andwhole-cell voltage clamp electrophysiological recordings of functionalactivity at AMPA receptors in acutely isolated cerebellar Purkinjeneurons (Bleakman et al., 1996, Mol. Pharmacol. 49; 581-585) and othertissues expressing AMPA receptors (Fletcher and Lodge, 1996, Pharmacol.Ther. 70; 65-89).

iGluR5 Antagonist Binding Affinity Profiles

Cell lines (HEK293 cells) stably transfected with human iGluR receptorswere employed. Displacement of ³[H] AMPA by increasing concentrations ofantagonist was measured on iGluR₁, iGluR₂, iGluR₃, and iGluR₄ expressingcells, while displacement of ³[H] kainate (KA) was measured on iGluR₅,iGluR₆, iGluR₇, and KA2-expressing cells. Estimated antagonist bindingactivity (K_(i)) in μM was determined for Compounds I-IV. As an indiciaof selectivity, the ratio of binding affinity to the iGluR₂ AMPAreceptor subtype, versus the binding affinity to iGluR₅ kainate receptorsubtype, was also determined. Compounds provided by the presentinvention displayed a binding affinity of at least 10 fold greater foriGluR₅ than that for iGluR₂, more preferably at least 100 fold.

EXAMPLE 3

The following animal model was employed to determine the ability of eachof the panel of compounds to inhibit protein extravasation, an exemplaryfunctional assay of the neuronal mechanism of migraine. The resultsobtained for the panel of compounds in this model are summarized inTable I (infra).

Animal Model of Dural Protein Extravasation

Harlan Sprague-Dawley rats (225-325 g) or guinea pigs from Charles RiverLaboratories (225-325 g) were anesthetized with sodium pentobarbitalintraperitoneally (65 mg/kg or 45 mg/kg respectively) and placed in astereotaxic frame (David Kopf Instruments) with the incisor bar set at−3.5 mm for rats or −4.0 mm for guinea pigs. Following a midline sagitalscalp incision, two pairs of bilateral holes were drilled through theskull (6 mm posterially, 2.0 and 4.0 mm laterally in rats; 4 mmposteriorly and 3.2 and 5.2 mm laterally in guinea pigs, all coordinatesreferenced to bregma). Pairs of stainless steel stimulating electrodes,insulated except at the tips (Rhodes Medical Systems, Inc.), werelowered through the holes in both hemispheres to a depth of 9 mm (rats)or 10.5 mm (guinea pigs) from dura.

The femoral vein was exposed and a dose of the test compound wasinjected intravenously (i.v.) at a dosing volume of 1 ml/Kg or, in thealternative, test compound was administered orally (p.o) via gavage at avolume of 2.0 ml/Kg. Approximately 7 minutes post i.v. injection, a 50mg/Kg dose of Evans Blue, a fluorescent dye, was also injectedintravenously. The Evans Blue complexed with proteins in the blood andfunctioned as a marker for protein extravasation. Exactly 10 minutespost-injection of the test compound, the left trigeminal ganglion wasstimulated for 3 minutes at a current intensity of 1.0 mA (5 Hz, 4 msecduration) with a Model 273 potentiostat/galvanostat (EG&G PrincetonApplied Research).

Fifteen minutes following stimulation, the animals were killed andexsanguinated with 20 mL of saline. The top of the skull was removed tofacilitate the collection of the dural membranes. The membrane sampleswere removed from both hemispheres, rinsed with water, and spread flaton microscopic slides. Once dried, the tissues were coverslipped with a70% glycerol/water solution.

A fluorescence microscope (Zeiss) equipped with a grating monchromatorand a spectrophotometer was used to quantify the amount of Evans Bluedye in each sample. An excitation wavelength of approximately 535 nm wasutilized and the emission intensity at 600 nm was determined. Themicroscope was equipped with a motorized stage and also interfaced witha personal computer. This facilitated the computer-controlled movementof the stage with fluorescence measurements at 25 points (500 mm steps)on each dural sample. The mean and standard deviation of themeasurements were determined by the computer.

The extravasation induced by the electrical stimulation of thetrigeminal ganglion was an ipsilateral effect (i.e. occurs only on theside of the dura in which the trigeminal ganglion was stimulated). Thisallows the other (unstimulated) half of the dura to be used as acontrol. The ratio of the amount of extravasation in the dura from thestimulated side, over the amount of extravasation in the unstimulatedside, was calculated. Control animals dosed with only with saline,yielded a ratio of approximately 2.0 in rats and apprximately 1.8 inguinea pigs. In contrast, a compound which effectively prevented theextravasation in the dura from the stimulated side would yield a ratioof approximately 1.0.

Dose-response curves were generated for each of the panel of compoundsand the dose that inhibited the extravasation by 50% (ID₅₀) or 100%(ID₁₀₀) was approximated. The respective ID₅₀ and/or ID₁₀₀ values, foreach of the panel of compounds employed in the present invention, aresummarized in Table I below. TABLE 1 Inhibition of Dural ProteinExtravasation (ng/Kg) Route of ID₅₀ ID₁₀₀ Compound administration(ng/Kg) (ng/Kg) I i.v.  6.5 (rat), —  4.0 (Gpig) — II i.v   15 (rat) —III i.v .0053 (rat) 0.10 IV(b) p.o — 0.01

1-22. (canceled)
 23. A compound which is 3S,4aR,6S,8aR Ethyl6-(((5S)-5-(Ethoxycarbonyl)-3-oxopyrrolidinyl)methyl)-2-methoxycarbonyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylate.